The present invention relates generally to surgical instruments and relates more specifically to a needle for implanting brachytherapy seeds within the body of a patient.
It is well known to treat tumors with localized radiation by implanting radioactive seeds within the body of the patient within or in the vicinity of the tumor. The seeds typically comprise I-125, Pd-103, or other suitable radioactive agents contained within a pellet or seed to prevent migration of the radioactive material throughout the body of the patient.
Such radioactive seeds, known as xe2x80x9cbrachytherapyxe2x80x9d seeds, are conventionally implanted within the body of the patient by advancing the seeds through a hollow needle. The needle includes a cannula having a leading edge for parting or cutting the patient""s tissue so as to dispose the cannula at a position to deploy the seeds with a push rod or stylet. Since it is usually desirable to implant a number of seeds in a single procedure, a plurality of seeds can be loaded into the cannula. To assure proper spacing between adjacent seeds upon implantation, spacers of cat gut or other bioabsorbable material may be placed between adjacent seeds. The stylet is then telescopically positioned into the rearward end of the cannula. This loading procedure is typically performed by a physicist, and the loaded cannula is given to a physician to implant the seeds in the patient. The physician inserts the cannula and stylet into the body of the patient to a location adjacent the tumor. The physician then holds the stylet steady and withdraws the cannula, causing the seeds and spacers to be pushed out into the tissues of the patient as the cannula is retracted.
A problem with this procedure concerns the need to load the seeds and spacers in the proper order. Once the loading procedure has begun, if the physicist is interrupted or becomes distracted, he or she may forget whether the last-loaded element was a seed or a spacer. Since it is not possible for the physicist to see inside the needle, there is no way to verify proper placement of the seeds and spacers without unloading the needle. Failure to load the seeds and spacers in the proper sequence, such as by loading two seeds without an intervening spacer or loading two spacers between adjacent seeds, can result in improper spacing of the seeds within the body of the patient.
Thus, there is a need for a needle for implanting brachytherapy seeds which permits a physician to verify proper loading of seeds and spacers into the needle.
The number and location of brachytherapy seeds used in a given treatment is carefully calculated to deliver a predetermined dose of radiation to the tumor. Since the amount of radiation delivered to a tumor depends upon the spacing and location of the seeds relative to the tumor, optimal brachytherapy treatment requires careful positioning of the seeds. A problem associated with prior art brachytherapy procedures is that friction between the brachytherapy needle and the tissues of the patient can cause the seeds to be improperly positioned. More specifically, as the cannula of the brachytherapy needle is retracted to expose the seeds in the tissues of the patient, friction between the outer surface of the cannula and the patient""s tissues causes the tissues to distend. The seeds are deployed into the distended tissue. When the frictional force is removed, the tissue subsequently returns to its normal position, causing the seeds to be displaced as the tissue moves. The seeds may thus not be positioned in the desired locations.
Thus, there is a need for a needle for implanting brachytherapy seeds which minimizes friction between the outer circumference of the brachytherapy needle and the tissues of a patient.
There is a further need for a brachytherapy needle which avoids the problem of deploying seeds into displaced tissue such that the seeds are displaced when the tissue returns to its normal state.
Stated generally, the present invention relates to a needle for implanting brachytherapy seeds into the body of a patient which addresses the foregoing concerns. In one aspect the device permits a physicist to visually verify proper loading of the seeds and spacers in the needle after the loading process has been completed. In another aspect the device minimizes friction between the outer circumference of the brachytherapy needle and the tissues of a patient so as to avoid the problem of deploying seeds into displaced tissue such that the seeds are displaced when the tissue returns to its normal state. The device operates in a conventional manner and thus does not require the physician to learn how to operate a new device. The device is also inexpensive to manufacture, thus providing advantages over conventional brachytherapy needles without significant increases in manufacturing costs.
Stated somewhat more specifically, the brachytherapy needle of the present invention comprises a hollow cannula defining a lumen through which radioactive seeds and spacers are delivered. A push stylet is telescopically received within the hollow cannula for advancing the radioactive seeds and spacers through the lumen of the cannula. In one aspect the hollow cannula has a window formed in a side wall through which at least a portion of the lumen can be visualized. In the preferred embodiment the window comprises a slot formed in the side wall of the cannula through which radioactive seeds and spacers can be viewed. Also in the preferred embodiment, a transparent covering, advantageously a sleeve of transparent, heat-shrinkable plastic, is disposed over the slot to prevent tissue from lapsing into the slot when the cannula is inserted into the patient""s body. In another aspect, a plastic outer sleeve of a lubricious material or having a lubricious coating minimizes friction between the outer surface of the needle and the tissues of the patient. Advantageously a single component functions as both the low-friction sleeve and the transparent window covering.